This invention relates to a method and apparatus for cutting parts from irregularly shaped and sized pieces of sheet material, such as for the particular case of cutting pattern parts for use in making shoes, clothing or upholstery from the leather of animal hides, and deals more particularly with an improved method and apparatus allowing pattern parts to be cut from irregularly shaped pieces of sheet material with a low expenditure of operator and machine time, with an efficient utilization of the sheet material, with the pattern pieces cut from the sheet material avoiding blemishes in the material and, if desired, with the parts being cut from the piece of sheet material within a thickness or other textural zone having a thickness or other textural characteristic matching the thickness or other textural requirement of the part.
The method and apparatus of the invention may be used in various different mass production situations where it is necessary to cut pattern parts from a large number of pieces of sheet material which vary in size and shape, which may contain randomly appearing blemishes and which may contain irregularly shaped zones of different thickness or other textural characteristics making it impractical or impossible to cut the same layout of pattern parts from each sheet. The invention, however, was initially conceived for use with the cutting of pattern parts from leather animal hides, and it is therefore for convenience hereinafter illustrated and described in association with such an application even though there is no intention to limit its scope solely to the field of hide cutting.
Since natural animal hides, when ready for cutting, are of various sizes and irregular shape and often include randomly distributed visible blemishes or imperfections such as scars, holes, scratches and burn marks, and also often include areas or zones of differing texture, such as surface appearance, thickness and softness; and since the requirements for the pattern pieces to be cut from the hides may be that no visible blemishes appear in the cut pattern parts or appear only in noncritical areas of such parts, or that certain pattern parts may or may not be cut from certain portions of the hide having textural constraints; the problem of efficient cutting of pattern parts is to arrange the required pattern part shapes as closely nested as possible within the usable periphery of the hide, while avoiding areas of the hide which contain blemishes, while at the same time having each pattern part placed on the hide within a zone having a textural characteristic suiting a related textural requirement of the part, so that the cut parts consume a maximum area of the hide and minimize the wasted hide surface between the cut parts, and so that the cut parts are also of the proper thickness, surface appearance and/or other texture characteristic taken into account in the layout and cutting of the hide.
In the past, a typical method of cutting pattern parts from hides was for a person equipped with die cutting tools, each much like a cookie cutter and corresponding to a desired pattern part shape, to examine a hide prior to its cutting and to then successively place the dies in cutting position on the hide and die cut parts from it by applying pressure to the die against a backup surface supporting the hide. In the overall procedure involving a typical irregularly shaped hide, commonly ten square feet to seventy square feet in area, the amount of hide wasted between usable parts cut from it was difficult to control.
The object of this invention is therefore to provide an apparatus and method for optimizing the usage of a hide or other irregularly shaped piece of sheet material in the cutting of pattern parts from it. A further related object is to provide such a method and apparatus which further allows the hide to be cut to avoid blemishes in the cut parts, or to cause the blemishes to fall into noncritical areas of the parts, and which method and apparatus also allows the parts to be cut from areas of the hide having one or more texture characteristics, such as thickness, meeting a corresponding one or more textural requirements of the parts.
More specifically, the object of this invention is to provide a method and apparatus which employs computer based equipment working interactively with a human operator or operators to define for each hide to be cut, the size and shape of the hide, the location of blemishes and the location of areas or zones having differing textural characteristics, to quickly provide a layout of pattern parts to be cut from the hide in which layout the pattern parts are arranged to optimize the use of the hide while avoiding blemishes and to assign the parts to areas of the hide suiting their textural requirements, and to quickly and accurately cut the pattern parts from the hide in accordance with the layout and, if desired, to label the cut parts and then separate them from the hide waste material, the method and apparatus of the invention in the aggregate providing a more efficient utilization of the hide than in the past as well as achieving a reduction in the amount of manual labor required in comparison with past methods and apparatus.